UNIT -3 TEACHING LEARNING MATERIAL

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BED 3 SEMESTER PEDAGOGY OF BIOLOGY

UNIT -3 TEACHING LEARNING MATERIAL

An outstanding, development in modern education is the increased use of supplementary

devices by which the teacher through the use of more than one sensory channel helps to clarify,

establish and correlate concept, increases knowledge, arouse interest, even evokes worthy

emotions and enriched the imagination of children.

Learning takes place at three levels - direct experiencing, vicarious experiencing and symbolic

experiencing.

Thus audio-visual materials are quite helpful in instruction. They supply a correct basis for

conceptual thinking. Researchers have recommended that in education we should appeal to the

mind chiefly through the visual and auditory sense organs. It is possible that 85% of our.leaming

is absorbed through these.

⮚ According to Gandhiji, "True education of the intellect can only come through a proper

exercise and training of bodily organs hands, feet, eyes, ears and nose.

⮚ Commenting on the use of A.V-aids, Kottari Commission 19964-66 observed that it

should indeed bring about an “Educational revolution” in the country. It further stated that

the supply of teaching aids to every school was essential for the improvement of the

quality of teaching

⮚ The NPE 1986 and as modified in 1992 has laid a great stress on the use of teaching

aids, especially improvised aids, to make Teaching learning more effective and realistic.

⮚ In the words of Edgar Dale, “Because A.V. materials supply concrete basis for

conceptual thinking, they give rise to meaningful concepts enriched by meaningful

association, hence they offer the best antidote for the disease of verbalism.".

EDGARDALE'S CONE OF LEARNING EXPERIENCES

Education, whatever are its goals and objectives, means and media ultimately has to result in

some form of learning or the other. Learning is essentially a modification of behavior due to

interaction of past experiences and present stimuli. The behavioral modifications arising out of

learning may take place in the three domains: cognitive, affective, sensory-motor (Psychomotor)

individually or collectively. It is well known that students in traditional classes don't retain

knowledge when it is simply given to them in the form of lecture and written material. Learners

tend to effectively retain material when their participation is high (achieve learning) and retain

less with low participation with course material (passive learning). Hence strategies need to be

developed to actively involve students in the classroom activity. In the 1960's the research of

Edgar Dale found that levels of effectiveness in learning are directly related to the participation

of the student. Dale developed a cone - shaped model that represents retention rates in

students for



different methods of course presentation. Concept of cone of Experience: Edgar Dale, the chief

exponent of A.V.aids in teaching is the originator, of the "Cone of Experience". All the Learning

experiences which can be utilized for classroom teaching are shown by Edgar Dale in a pictorial

device-"Pinnacle form” - which he called the “cone of experience" if we go up the pinnacle from

its base, we find that every aid has been arranged in the order of increasing abstractness or

decreasing directness. In a simple language it may be stated that the cone' classifies the

A.V.aids according to their effectiveness in communication-aid at the base of the cone as "most

effective” – relative effect gradually decreases.

Dale proposed that learning is stimulated progressively form concrete (ile, hand on) experiences

to abstract (i.c verbal and visual) symbols. His cone is most useful as a guide for introducing

and building concepts. At the most basic and effective level of instruction students are

introduced to new material through an actual “hands on experiences or doing the real thing.

“Students see, do and talk about the concept. Learning will be effectively completed conditions

the fulfilled. At the top of the cone, or triangle is lecture and text. Dale's model suggest that

these passive instructional modes are the least effective ways to introduce new concepts to

students. Between top and bottom of the cone, Dale has several other levels of instructions

including giving a talk, watching a demonstration, seeing a film or picture.

The cone of experience as a model has eleven bands. The model suggests a comparative

approach to effective teaching learning process. The model shows a progression of learning

experiences from direct purposeful experiences to abstract verbal expression.

The experiences included in the cone are indicated below i.e. all the experiences that the

human beings derive are mainly from three sources.

a. Direct, Purposeful experiences: The experiences gained through direct contact with senses

are direct and purposeful i.e. the experiences gains through handling, testing, touching,

travelling etc. "An ounce of experiences is better them a tone of theory" and hence experiences

is the best possible method of teaching effectively. Thus form the base of the Cone.



b Contrived experiences: A contrived experience is an imitation of reality. It is like a working

model, which is a replica of reality and differs from the original in either size or its complexity. It

is not possible to present a real object event in all cases. In some cases the real object may be

too big, very minute, concealed etc. In such a situation imitation is preferred for better and

easier understanding.

Dramatic Participation: Dramatic participation is a mean by which certain real events are

represented so that we can get close to reality as possible. Thus we participate in a

reconstructed experience as close to the original as possible. Puppet shows, pageants (kind of

community drama, usually based on history) Pantamine (actors do not speak, make

movements), tableau (Picture line science in which the characteristics stand still, silently) mock

conventions, plays are various forms of dramatization. The experience is more useful when one

actively participate rather than merely watch it. A keen observer gets the feeling of being in the

actors shoes.

A perusal at the Dale's cone of experiences shows that the tip of the cone represent the verbal

symbols which are abstract and difficult forms of classroom communication. And the bottom of

the cone represents Direct and purposeful experiences. So in order to make the classroom

communication meaningful, the teacher have to move away from excessive use of verbal

symbols and make use a variety of teaching resources which are available around them. Then

only the teachers role would shift from conventional knowledge dispenser to resource manager

and facilitator of learning.





AUDIO-VISUAL INSTRUCTIONAL AIDS

Introduction:

There was a time when a great part of learning was only linguistic, i.e. it was thought to be a

communication by the word of the month. Language was, and it still remains the most effective

tool in the learning and teaching. The recent trends have seen many new trends in the media of

teaching and learning. “In addition to the language tools certain mass media are now gaining

acceptance under the general leading of A.V.aids.

Thus an outstanding development in modern education is the increased use of supplementary

devices by which the teacher through the use of more than one sensory channel helps to clarify,

establish and correlate accuracy, concepts, interpretations and appreciations, increases the

knowledge, arouses interest and even evokes worthy emotions and enriches the imagination of

children.

Learning takes place at three levels -- direct experiencing, vicarious experiencing and symbolic

experiencing. Thus A.V. materials are quite helpful in instruction. They supply a concrete basis

for conceptual thinking. They give rise to meaningful concepts to words enriched by meaningful

associations. Researchers have also recommended that in education we should appeal to the

mind chiefly through the visual and auditory sense organs, since it is possible that 85% of our

learning is absorbed through these.

What are A.V. Aids?

There are times when firsthand experiences cannot be given to students and it is then, a

teacher uses substitutes for reality - photos, models, maps etc. There are substitutes which

attract vision and hearing of the students. As such term “Audio-visual aids” has been formed

(Audio-to hear and visual - to see) i.e. those instructional devices that can be heard as well as

soon.

According to Carter A.Good "Any device by means of which the learning process may be

encouraged or carried on through the senses of hearing and sight simultaneously” is known as

Audio-visual aid e.g. Sound film, slides, sound motion pictures, television etc.

Burton says "Audio-visual materials are those sensory objects or images which initiate,

stimulate, and re-in force learning." The following diagram may be helpful in clarifying the

meaning:

WHAT IS AN INSTRUCTIONAL AID

An instructional aid' is any device that assists an instructor to transmit to a learner facts, skills,

attitudes, knowledge, understanding and appreciation.



A visual aid is an instructional device that can be seen but not heard. An audio aid is an

instructional device that can be head. An audio-visual aid is that device which can be heard as

well as seen.

The child is interested to see concrete things. He wants to handle, manipulate and the teacher

should provide occasions for the pupils satisfy their curiosity of doing things. The learning

though sense is more permanent than mechanical learning. Out of five senses it is through the

hearing and seeing that 86% of knowledge is gained.

THE VALUE OF AUDIO-VISUAL AIDS TO LEARNING OR IMPORTANCE OF AUDIOVISUAL

AIDS

Audio-visual aids are instructional devices which can be heard as well as seen. These aids are

intended to impart knowledge to pupils through senses to ensure quick and effective learning. A

teacher has to make use of the aids in order to make his lesson more interesting and real. We

learn through the senses and the senses of sight and hearing have a greater share in this

process. Man depended upon the sight long before he felt the need of speech and that the

alphabet was derived from the picture sign language. But it should always be borne in mind that

these aids should be used as aids to teaching and should not replace the teacher but

revolutionize other methods of teaching.

1. A.V. Aids are potent starters and motivators:

A.V. Aids are best attention compellers. They arouse interest and motivate the pupils to action

and stimulate physical and mental activity. When the child finds learning made easy, interesting

and joyful with the help of sensory aids he feels motivated. He cannot but attend to an

interesting procedure going on before him. It enables the students to learn faster, remember

longer, gain more accurate information and receive and understand delicate concepts and

meanings. Thus learning becomes meaningful, enjoyable and effective.

2. A.V. Aids give variety to classroom technique:

A.V. Aids represents a change from the traditional activities of the school. While using them the

child is experiencing something different. Variety is always attractive to the child as well as to

the adult. A.V. Aids provide a change in the atmosphere of the classroom. They allow some

freedom from the formal instruction of the traditional type. While using aids the pupils may move

about, talk, laugh, question, comment upon and in other ways act in a natural manner as they

do outside the classroom.

3. Many of the aids provide the child with opportunities to handle and manipulate:

An opportunity to touch, feel, handle or operate a model, specimen, picture, map, press a button

or turn a crank gives an added appeal because it satisfies, temporarily at least the natural desire

for mastery and ownership

By reviewing and rehearsing the aids used pupils get opportunity to correct misconceptions and

secure additional ideas. A film after having been shown to the students can be reviewed by the

active discussion among the students and with the teacher. By showing the film again the pupils



correct their mistakes and get a chance to revise what they have learnt and at the same time

gather additional information which they had unconsciously overlooked.

4 Saves time: - It saves time and learning is more solid and durable. The pupils learn about

35% more in given time and the knowledge learnt is retained for 55% longer time.

5. Provides firsthand experience: It extends firsthand experience when the students see a

demonstration, handle the apparatus, perform the experiment themselves and prepare charts,

sketches and models.

6. It brings reality to the classroom: It helps in bringing vivid reality into the classroom. Mere

chalking and talking do not help much and it is important to make use of the aids.

7. It is the most natural and easiest way of learning: Image is the greatest instrument of

instruction. When a child sees an object he forms an image of that object.

8 It is a representation of the real source: Though firsthand experience is the most educative

type of experience always it is neither desirable nor possible for the pupils. In some cases the

actual material is inaccessible very expensive, or physically, so constituted that they cannot be

easily studied. So at such occasions it becomes essential to provide a representation, of the

real resource. If it is readily available and less expensive, it may be even more desirable. For

example, it is not desirable that the students should have the direct experience of recognizing

the characteristics, actions, affects, and remedies of any fatal disease, say plague typhoid etc. It

is always useful to give them vicarious experience. Similarly it is not possible for everybody to

climb up the Everest but the children have vicarious experience of climbing even by seeing a

film. So in such situations reproduction is better for the original may be too complex, too large,

too small, too slow, to be successfully experienced firsthand.

9. Simplifies teachers work: The large number of pupils and shortness of teachers require some

aids that can simplify teacher's work.

10. Now curriculum have broadened and extended the field of education which can be

satisfactorily covered only with the help of teaching aids.

11. Provides opportunity to inculcate scientific attitude: It provides opportunity to inculcate

scientific attitudes and give training in the scientific method.

12. They supply the context for sound and skilful generalizing: Books lack the specificity, the

warmth, indeed some of the unutterable poignancy of concrete experiences. Through direct,

purposeful, first hand experiences and semi concrete A.V. experiences we can supply the

context for sound and skilful generalizing.

13. A.V. Aids can play a major role in promoting international understanding: These aids can

bring about mutual understanding and appreciation of cultural values and ways of living among

the different nations of the World. Enlightened and sympathetic attitudes can be developed

among the school children through this media. Films and radio programmes can be exchanged

among the different countries. Coloured slides on works of art of different countries lead to

mutual appreciation of eastern and western cultural values. To conclude in the words of

Mckown and Roberts “A.V.Aids wisely selected and intelligently used, arouse and develop

intense and beneficial interest and so motivate the pupils learning. And properly motivated

learning means improved attitudes, permanency of impressions, and rich experience and



ultimately more wholesome living.

PRINCIPLES FOR THE SELECTION AND USES OF AUDIO-VISUAL AIDS

In the teaching process, emphasis is laid on the use of A.V. aids because of their multifarious

values in making the teaching learning process interesting and effective. But wrong use of these

aids will invite adverse criticism. So precautions must be taken while selecting and using these

aids. Some of them are discussed below. Principles for Selection:

1. The aids should be integrated with learning. It should be an integral part of educative process

and appropriate to the curriculum of the class. It should not be merely recreational but should

accomplish some significant end and co-ordination with day to day lessons. For example while

teaching about a scientist the tape recorded speech may be reproduced in the classroom. This

will provide life like situations and the pupils will feel interested.

2. It should be according to the age, intelligence and experiences of the students. It should

neither be too simple nor too complex. It should suit to the physical, psychological, intellectual

and social development of the group with which it is used.

3. The language should be familiar and understandable to the pupils.

4. It should be truthful, accurate and realistic and should be a substitute for reality. For example,

a model of red-rose should represent a true flower in its proportion, colour, symmetry etc. If the

aid used is just a misrepresentation of the actual thing the whole aim of the aid or teaching is

defeated for the children will learn wrong things.

5. It should be motivational and highly informative. The aid used should attract and capture the

attention of pupils.

6. It should be available where and when required.

7. It should have desirable utility and should be according to local conditions and needs. The aid

selected should satisfy the purpose for which it is used.

PRINCIPLES FOR USE

1. The teacher should be well skilled in the use of aid.

2. It should be actually taught and not merely displayed.

3. It should not substitute but supplement the teacher & work.

4. While using the aid active participation of the student should be sought.

5 It should be properly protected and preserved for nothing discourages or masks the interests

of the students more than a spoiled picture, broken model or a cracked slide. .

6. It should be located conveniently so that it is easily available when need arises.

7. It should be evaluated at regular intervals in order to know their use and effect on learning.

ESSENTIAL QUALITIES OF TEACHINGAIDS

1. Accurate: If the aid is the actual object then it is very essential that it is accurate, in its

representation. Charts and models sometimes tend to be in accurate. Charts lack third

dimensions, photos are very accurate but they can't be used to show all the details because



they may overlook the essential features. So while using aids teacher should know that they are

proper and adequate for specific lesson. The aid must not give incorrect concept.

2. Relevance: The aid should be relevant and directly related to the subject-matter. It should be

accurate in detail, understandable and interesting

3. Realistic: Aid may be anything from crude diagram to an actual object. But ifit seems to be

realistic, its virtue increases. It has been said that visual aids have value in proportion to the

degree of realization.

4. Comprehensible: The students find it difficult to understand those aspects which the teacher

wants to bring home. These aspects may be overlapped by other unnecessary facts, for

instance in metallurgy if the students are shown real plant of that metal under study, they do not

completely understand. They visualized real object. It is relevant but due to its complexity they

may be confused. So the aid should neither be very simple nor too complex. Both types cause

loss of interest .

5. Interesting: It should create interest in the students.

6. Simple: Should not be overcrowded.

7. Cost: It should be economical.

8. Availability: It should be available when required

9. Preparation: The teacher should be well prepared for the use.

10. Big enough: It should be large enough to be seen by all

11. Location: It should be located at a place where it can be easily seen.

12. Evaluation: It should be evaluated at regular intervals in order to know its effect.

13. Appropriate: It should suit to the age, intelligence and experience of the students.

Psychologically the A.V. aids are important for their significant role in strengthening memory.

These aids make for sense participation, thus opening the gateway of knowledge to help the

child overcome forgetting.

In fact, the total intellectual activity itself is based upon sense perceptions and the old Chinese

saying that a single picture is worth a thousand words is not an empty speech. The sensory aids

helps the child in self-expression of various forms which is undoubtedly helpful in learning. And

it is further true that whatever is made to appear before our eyes leaves better imprint on our

mind than otherwise.

Thus these A.V. Aids are means that can be employed to teach pupils what words mean and to

aid them in critical thinkings which is the basis of the higher forms of learning

WHERE AND WHEN TO USE A.V. AIDS

The success of these aids depends mostly on the appropriate use to which they are put. We

have to use them only where/when they can add to the clarity of the subject e.g.

1. Where the object is too far distant to be actually seen as in Geography and astronomy.

2. Where the object is far removed in time as the history (viz. discovery of O, atom etc.)



3. Where the object is too big to be brought into the classroom e.g Bhakra Dam, an aeroplane

etc.

4. Where the object is too small to be seen by a naked eye og germs, structure of an atom.

5. Where the object is too slow to be seen e.g germination of seed, growth of a plant.

6. Where the object is non-visual like sound waves, electricity etc. 7. Where the object is too

complex to be understood in its natural form e.g., manufacturing of glass, cement etc.

WHY TO USE A.V. AIDS IN SCIENCE TEACHING

1. To present exotic material i.e. the rare materials which are not seen.

2. To present historical method.

3. To present information about in accessible places i.e. places where we can't go.

4. To give bird's eye view

5. Amplify sounds.

6. To acquaint the people with dangerous situations or conditions e.g. volcanic eruption etc.

7. It substitutes firsthand experience.

8. To minimizes the time (About 40%)

9 To bring the child to reality.

10. To bring variety to classroom.

CLASSIFICATION OF TEACHING AIDS

It is rightly said that senses are the gateways to all knowledge and sensory learning

experiences make instruction efficient, effective and lasting. The human senses provide

concrete learning experiences by converting the abstract ideas into direct purposeful activatec.

Based on the sense organs involved teaching aids can be classified as follows.

I Classifications based on sensory organs:

Audio-visual aids can also be grouped into three broad categories viz. Auditory aids or audio -

aids, visual aids and audio-visual aids.

1. Audio Aids: An aid or a teaching device that can be heard is known as an audio aid eg.

Audio-tapes, cassettes, etc.

2. Visual Aids: An aid or a teaching device which can be seen but not heard is known as visual

aid. Eg: audio-tapes, cassettes, etc

3. Audio-Visual Aids: An aid that can be heard as well as seen is known as an audio-visual aid

Eg: motion pictures, video cassettes, TV, etc

II. Teaching aids can further be divided into three categories.

1. Graphic Aids: Eg: Charts, posters, picture, cut outs, placards, flash cards, flannel board chalk

board, bulletin board etc.

2. Three-dimension: Eg: Models, Specimens real objects, apparatus exhibits, and diagrams. 1

3. Activity Aids: Eg: Demonstrations, dramatization, projects, excursions, field trips, role play

etc.



III. Classification on based on dimension of objects:

Based on dimensions teaching aids can be classified into two types.

1. Two Dimensional Aids: Teaching aids having only two dimensions (length and breadth) are

known as 2-Dimensional teaching aids. Eg: Charts, Graphs, Maps.

2. Three Dimensional: Teaching aids that have 3-Dimensional (length, breadth and depth or

height) are known as 3-Dimensional Teaching aids. Eg: Models, Objects, Specimens, Puppets

etc.

IV. Based on Experiences:

Based on experiences teaching aid each be classified into three types.

1. Direct-Experience: First hand experiences that the child gets through learning by doing are

the Direct Experience. Eg: Laboratory, by doing practical, visit to places of interest.

2. Representative Experiences: Something it is neither possible nor desirable to use direct

experience as they are either too expensive or beyond the reach. Then we Represent them i.e.

the object or items that cannot be brought to classroom are shown with the help of charts,

models, pictures, film etc.

3. Verbal or symbolic experience: These are the verbal or oral and sometimes written

experiences history, feelings etc.

V. Based on qualities:

Based on qualities teaching aids are divided into.

1. Visual Aids:Eg charts, diagram bulletin boards, models, slides etc.

2. Auditory Aids: Eg: Radio, tape-recorder, gramophone.

3. Audio-Visual Aids: Eg: T.V. motion films etc

4. Activity Aid: Eg: Museums, Excursions, Aquarium, Vivarium etc.

VI. Classification based on the type of projection while using Teaching aids.

Based on the mode of projection or non projection teaching aids i.e visual aids are classified as

projected and non-projected aids respectively.

1. Projected Aids: Those aids which help in projecting visual on to a screen are known as

projected aids.

2. Non-Projected Aids: Visual aids which do not help in their projection on to a screen are

known as non-projected aids.



VIL. Classification of teaching aids

Based on the principle of movement or motion there are two kinds of teaching aids - static and

dynamic aids.

1. Static: Those aids used in class-room Teaching which do not move and the visuals are at rest

are known as static aids.

2. Dynamic: Those aids in which visuals or parts are capable of being made to move by

mechanical principles are known as Dynamic Aids.

NCERT classification of Teaching Aids;

The NCER bulletin of AV aids classifies the teaching aids into 6 types. They are 1) Projected

aids, 2) Graphic aid 3) Display board 4) 3dimentional 5) A.V. aids and 6) Activity aids.



VIII. Based on size of Media:

Based on size of media Teaching Aids as are classified into two types.

1. Big Media: Includes computer, TV, VCR, etc

2. Little Media: Includes Radio, filmstrips, graphics, visual, audio, cassette etc

5. Based on Number of Sense organs used:

Depending on the number of sense organs used, teaching aids are classified into two types.

Unimodal Aids: Aids in which only one type of sense organ (either visual or auditory) are used

are called unimodal aid.

b. Bi-modal Aid: Aids in which both the sense organs are used (visual and auditory) are called

Bi-modal aid.

TEACHING AIDS

Aids are a supplement to teaching, bringing up to date and expert knowledge to the classroom.

They strengthen the spoken or written words with concrete images. They provide rích

experiences. They contribute to the depth and variety of learning and thus makes learning

permanent Thus the teacher can do a lot in his job of teaching with the help of teaching aids.

Some of the important teaching aids that are commonly used in sciences are

CHARTS

A chart is a sheet of any kind on which the information is exhibited in different forms.

It is defined as a visual symbol summarizing or comparing or contrasting or performing other

helpful services in explaining subject matter.

Charts are the graphic teaching material including diagrams, pictures, graphs, maps etc. It can

also be defined as illustrative visual media for depicting a logical relationship between main

ideas and supporting facts. According to kinder "charts are the graphic aids depicting

information in the form of tables pictures, graphic and diagrams.”

Readymade charts are available for use in teaching in almost all areas of the subjects. But

teacher can prepare charts by themselves very easily incorporating their own ideas and lines of

approach of the specific topic.

Purpose of Charts: Charts serves the following purposes

. 1. Shows relationship by means of facts and figures.



2.. Summarizes information.

3. Presents the material symbolically

4. Shows continuity in process.

5. Presents abstract ideas in visual form.

6. Shows development of structure.

7. Stimulates thinking

8. Motivates the Students.

9. Enhances the power of observation.

Important points in making chart:

A teacher should keep the following points in mind while preparing charts.

1. Use full sheets

2. Use only one side of the sheet

3.. Draw margins

4. Label it correctly

5. Use light colored charts and dark colored pencils.

6. Display information about one concept only on the chart.

7. It should not be over crowded i.e. too many details should not be there in charts.

8. Labeling should be big enough so that all students can see at the back.

9. It should be neat in appearance.

10. It should be attractive.

11 Straight pins, peg board clips, gummed hangers may be used for fastening charts without

damaging them.

12. Do not use fluorescent colours, since they are not visible.

13. Do not use too many colours.

14. Do not decorate the chart

15. Charts should be relevant to the topic. [Topic Specific)

16. It is better to draw a rough plan of the chart before preparing it.

17Charts may be backed up by pasting gauze cloth on the back with sadhesive paste to make it

strong.

18. Reapers of any light wood of cross section will make the chart stay Paflat when hung

19. For suspension, eyelets with coloured thread may be provided on the top reaper.

20. There should be some provision for hanging the charts in the classroom.

21. Use a pointer while teaching or showing chart.

22 Store the charts carefully for future use also.

Types of Charts:

1.Flip Charts: A series of charts containing visual information about the same area of knowledge

is known as flip chart.

2. Flow Charts: Flow charts show the functional relationship between the different aspects or

parts of the unit, process etc. The flow chart must show where a division actually stands

relatively in a given system c.g. classification of plants or animals can be represented by flow

chart.



3. Tabulation chart or table chart or Tabular charts: Here data is presented in a tabular form. It is

used for comparison or for listing advantages and disadvantages. It represent the data in

ordinary sequence. School time table is a good example of table chart.

4 Time Charts: This charts provides a chronological frame work within which events and

developments may be recorded. They develop a sense of time among the pupils, and helps

them to comprehend and visualize the pageant of time and its relationships.

5 Tree Charts: A chart made in the form of several branches from the trunk of a tree is known

as tree chart. The main idea is represented in the form of trunk while the branches represent

various developments, relationships or sub-parts of the main idea. This charts are also known

as genealogy charts.

6 Guidance Charts: These represent a simple statement for students/ teachers or others to

understand and follow.

MODELS

A model may be defined as three-dimensional representations of real rings. As they have 3-

dimensions i.e. height, width and depth they are nearer to reality. As such they make the

understanding clear, easy and better. Models also provide the knowledge of the internal and

well as external parts of a things which is not possible with the charts and twodimensional aids.

Models can be handled operated and seen from a number of angles.

Big models of small things can make its structure and working easily omprehensible to the

students. Besides this small models of big things an bring reality to the class room.

Types of Models:

Models can be classified into the following types.

1. Simplified models or solid models: These models are not made to exact scales. It is just a

replica of the original, made with suitable material like clay, plaster of Paris, wood etc. to show

the external parts and features of the things. As it is made of the solid material, it is known as

solid models e.g. models of vegetables, fruits, dolls, toys.

2. Scale Models: In order to form a correct idea of an object (Say a dam or projects) scale

models are used.

3. Working models: These modes are used to demonstrate in a simple way an operation of

process. These models are either actual working things or their miniature replicas. For example,

the working model of excreatory system gives a thorough understanding of its various

operations and hence have great educational significance.

4. Cross-sectional models or cut-away models or X-ray models: These models are replicas

of the original things to show internal parts of a thing i.e. they show the inside of an object. They

may be either in the form of a cross-sectional model showing internal parts of a thing or may be

composed of detachable parts. They are difficult to make in the schools as their require

expertise to construct. They are of immense use in teaching technical subjects also e.g. cross

"sectional model of human body, petrol engine etc.



5. Sand Models: Sand models are made using coloured sand. These are the graphic lay-out

using sand, clay, saw dust and other objects to show houses, trees, rivers etc. They are made

using coloured sand in a tray or on tables. Generally green fields are shown by covering area

with green sáw dust, water with blue cello flame and cardboards cut outs for showings trees,

forests etc. e.g. A tribal village, a city area, a forest area etc.

The use of models becomes essential in certain situations like

1) When the real thing is not available in that season.

2) When the real thing is too big.

3) When the real thing is too expensive

4) When the real thing is too far

5) When the real thing is too dangerous to handle.

6) When the real thing is too small.

7) When the real thing is too delicate.

SPECIMENS

A specimen may be defined as a typical object or part of an object. which has been removed

from its natural setting and environment. There are certain organisms or material that cannot be

studied in their natural habit or brought live to the laboratory for e.g. snakes, a part of a huge

rock etc. To study them, we need other alternatives. Specimens are one such alternative.

Various types of algae, fungi, bryophytes, pteridophyles, leaves, stem flowers, twigs, fishes,

snakes, insects, mollucks, bones of frog, bones of rabbit are collected and preserved for study

in the laboratory. All these objects are called as specimens. These are the objects, which were

once living and were collected either in the living form or after their death and preserved for

study.

These teaching aids are powerful interest arousing devices which possess the capacity of

involving all the five senses - tough, sight hearing, smells and taste. Objects and specimens are

the real thing and their use in the classroom imparts direct or firsthand learning experiences to

the children.

Sources of objects and Specimens:

1. Nature: It is the best source for the collection of wild flower, leaves, twigs, fruits, grains,

shells, stones, insects, butterflies etc. They can be collected during field trips.

2. Local Market: It is a good source for buying low-cost objects:

3. Manufacturers: Specimens can be procured from the manufacture also.

Mounting of the Specimens:

The first step after the collecting of the specimens is to mount then properly. The following

procedure may be adopted for mounting.

1. Small objects and specimens can be mounted by pasting them with adhesives, wire, nails,

cello tape on cardboard.

2. The collection of grains and seeds can be kept in small sized bottles or small polythene bags

and stuck on to the cardboard using quick fix adhesives.



3. Rocks, minerals, shells may be kept in cardboard boxes which is divided into small square

compartments.

4. Botanical specimens after they are pressed and dried can be stuck on the pages of a drawing

book.

5. Animal specimens like birds may be stuffed and mounted properly and can be kept in glass

cases of suitable sizes or in wooden boxes.

6. For zoological specimens like butterflies, moths and insects, boxes lined with cotton may be

used for mounting. Naphthalene balls should be kept in them to preserve them.

All animal specimens should be disinfect with DDT or spray of other strong disinfections and

kept in the show cases sealed properly.

After mounting, the specimens should be labeled (like name of the specimen, collected by,

place of collection, date of collection etc.) and then catalogued.

Preservation of Specimens:

The next step is the preservation of the collected specimens. The following procedure may be

adopted for preserving the specimens.

1. Plant specimens like roots, stems, leaves, flowers, buds, inflorescence, fruits etc. may be

preserved in the glass jars by making use of appropriate chemicals like formaldehyde (10%).

2. Plant specimens can also be preserved in the form of temporary, acpermanent slides.

3. Animal specimens life histories of mosquitoes, houseflies, silkworm etc. may be properly

mounted on glass strips and kept in jars filled with 10% formaldehyde.

4. An aquarium may develop to study the behavior of fishes and other aquatic organisms.

5. A Vivarium can be developed for studying the different types of caterpillar, silkworm,

butterflies and other insects living in the air. 6. A terrarium can be developed for keeping

animals such as earth worms, frogs etc. So that they can be preserved in their natural habits. 7.

Different kinds of snukes, molluscs, lizards and fishes can be kept preserved in the properly

sealed jars filled with 30% formalin solution. 8. All animal specimens should be disinfected

before keeping in the showcases.

Displaying the Specimens:

After collection, mounting and preserving, the last step is displaying of the specimens. The

following procedure may be adopted for displaying them.

1 All collected specimens must be classified into different categories like plants-roots, stems,

leaves, animals - fishes, mammals etc.

2. Every specimen must be properly labelled before keeping in the laboratory or museum. The

following information should be used for labeling

1. Name of the specimen

2 Name of the collector

3 Brief description

4 Place of collection

5 Date of collection



3. After labeling, the specimens should be display properly in an order in the laboratory or

museum. For this the schools must have the laboratories or the museum.

Advantages of specimens and objects:

The advantages of specimens may be broadly categorized into two types.

1. Advantages of collecting the specimens

2. Advantages of specimens while using as a teaching aid.

1. Advantage of Collection:

a) The collection of the specimens by the students itself is an interesting educational

experience.

b) Students power of observation and first hand experiences are enhanced by the collection of

specimens.

c) By collection of specimens, mounting and displaying the students derive a kind of

satisfaction.

d) Collection helps in developing social skills as the students have to interact with others like

teacher, other students etc.

2. Advantages of specimens as a teaching Aid:

The advantages of using specimens as teaching aids in the classroom are:

a) "They being real and 3-dimensional are provides real, direct and first hand experiences to the

students.

b) They involve all the five senses in the process of learning.

c) They develop observational skills of students.

d) They arouse interest in the class-room.

e) They make the class lively

Using specimens in the classroom:

While using specimens as the teaching aid the teacher must keep the following points in mind.

1. Plan the teaching with direct observation of the specimens, that are to be used.

2. Do not just display the specimens, but teach them.

3. Try to illicit the finer details of the specimens from the students by asking questions.

4. Emphasise on the important structural details while using specimens.

5. Review the specimens again and again to make the learning permanent.

ACTIVITY AIDS

The activities or the learning situations in which students participation is involved can be called

as an activity aid. There are many learning situations in which students participation through

direct experiences can be incorporated. These activity aids puts the students in the role of

active seekers of knowledge.

1. AQUARIUM

The term “aquarium” is derived from the combination of two latin words “aqua” meaning water

and “arium” meaning a place for relating to. So the literal meaning of aquarium is a place where

plants and animals specially fishes are placed in water. It is called artificial Ecosystems. So an

aquarium is an artificial pond made of glass tank supplied with a light source in which aquatic



plants and animals are kept alive for study or for beautification purpose.

An aquarium in the classroom creates an environment for the study of science. The young

people usually like to observe the movement of animals, their colour, and voice. Birds and fish

are excellent substitutes to satisfy the curiosity of the young people. An aquarium may represent

complete natural environment. It is beautiful to look at and a valuable aid to study small aquatic

plants and animals. The pupils get an opportunity to acquire first hand experience of many

interesting events of aquatic animal life. They can observe and studý plant animal relationship.

The pupils can see how the aquatic animals and plants collect their food; how they grow, how

they reproduce and how they interact to external stimuli.

Setting up an Aquarium:

The aquarium is usually a rectangular glass box; and it can be easily made by the teacher. The

classroom aquarium should-be sufficiently big. The aquarium helps pupils acquire valuable

concepts such as; water contains dissolved air (02), many plants and animals live in water,

plants and animals are interdependent, fish have special organ for moving freely a in water etc.

While setting an aquarium, it should be cleaned and a layer of sand, of about one inch

thickness, should be spread at the bottom. Over it a layer of small stone pieces should be

placed and then covered with some other materials such as shells. It is then filled with water.

The aquatic "plants such as vallesnaria, hydñlla, moss should be placed before' snails or fish

are put in it. It should be noted that neither too many plants nor too many fish should be put in

the aquarium.

Guidelines to be followed for forming and maintaining an aquarium:

1. Clean and keep the aquarium dust free.

2. Place one or two inches of sand to cover the bottom of the aquarium tank.

3. Always pour clean pond water into the aquarium tank.

4. Keep it exposed to strong diffused sunlight.

5. Use animals which can get along together.

6. Keep a constant watch on it and remove any dead animals at once.

7. Feed the animals sparingly.

Precautions for maintaining aquarium

1. It should have a permanent place in the lab.

2. Water in it should not be frequently and unnecessarily changed.

3. Use only healthy specimen and any contaminated specimen be given a potassium

permanganate bath for about half an hour.

Uses:

1. It is very helpful in teaching concepts related to ecology.

2. Students can directly observe the locomotion of aquatic animals.

3. It helps to develop a love, for animals in students.

Types of Aquarium:

1. Fresh water aquarium: It is the most popular and it is easy to maintain.



2. Marine aquarium: It requires complex equipments to set up and maintain. It features a diverse

range of invertebrates.

3. Brakish water aquarium: It combines the elements of both fresh water and marine fish

keeping Fishes kept in brakish water aquarium generally comes from habitat with varying

salinity such as mangroves and estuaries.

4. Reef aquarium: It is a marine aquarium that houses corals.

5. Community tank aquarium: It is the most common type of aquarium where several non-

aggressive species are kept together.

6. Aggressive tank aquarium: In this aquarium a limited number of species that can be

aggressive towards other fishes are kept.

7. Species or specimen tank aquarium: It usually have only one fish species, along with plants.

This type is useful for fish that simply cannot be housed safely with other fishes such as the

electric eel.

2. VIVARIUM

Vivarium is usually an enclosed area, for keeping and araising plants and animals for

observation or for scientific study or for research purpose. According to Oxford Dictionary “A

place specially adopted or prepared for keeping living animals under their normal conditions,

either as subjects of interest or for the purpose of scientific study frequently in later use is called

a vivarium".

A vivarium can be a very large structure, possibly an outdoor one or it can be a small one like

an aquarium to keep on a desk or a table. An indoor vivarium is an excellent educational activity

as the students can study about the habitats, needs of the species, interactions of the species.

Setting up a Vivarium:

1.Take a small jar or an aquarium tank.

2. Put soil at the base.

3. The soil should provide food matérial (Organic matter) to the organisms but supplementary

feeding can also be given.

4. Then put a dish of water.

5. Air is not a problem.

6. Organisms like snails, reptiles, snails and amphibians with their representative plants can be

kept in the Vivarium.

7. Place the vivarium in a cool plaće away from the sun.

3. TERRARIUM.

A terrarium represents a complete land environment just as an aquarium represents the

complete water environment. Its size may vary according to purpose. Ordinary aquarium

containers may also be used for terrariums, but a glass container, large enough to hold a few

plants and small animals can ‘serve the purpose. For young children á terrarium is as interesting

as an aquarium and in addition, a terrarium permits greater variation in the types of environment

to be illustrated.



It may be arranged to represent a bog-type terrarium showing how plants and animals live in

wet places or may represent- plants and animals of hot and dry lands; or it may contain certain

plants and animals living at different elevations on the surface of the earth.

Preparing a Terrarium:

A terrarium may be prepared like an aquarium. At the bottom, a layer of sand and small stones

should be placed. Around the edge of the base of the container, a band of moss may be placed.

A handful of charcoal may be scattered over the sand layer to act as absorbent. Then it is

covered with a few inches of moist loamy wood soil prepared by mixing soil or sand with

decayed leaves. Over it, different plants and small animals should be housed. A few rocks and

fungus-bearing branches of trees add to its effectiveness. If desired, a small artificial water pool

may be prepared. Small toads, lizards, and other locally available insects and animals may be

placed in it. In addition to mosses and ferns, locally available slow-growing plants should be

raised. The terrarium needs occasional watering. Too many plants and animals are to be

avoided.

A terrarium, if properly arranged, serves as a good instructional medium. It is interesting,

attractive and cheap; it contributes to learning various concepts regarding plant and animal life

on the land surfaces.

Some of the important types of terrarium are:

1. Swamp Terrarium: It is suited for animals that live on the ground e.g. Salamander species

and water-loving frogs.

2. Woodland terrarium (Tropical rainforest): It is a warm and humid terrarium suitable for

keeping ferms, orchids as vegetation and tree frogs, and little toads can also be kept.

3. Steppe-Terrarium (Rock-Terrarium): It is a terrarium with lots of sand rocks and firm plants. It

is suitable for keeping wall-lizards, and large plants.

4. Mixed Terrarium: In a mixed terrarium several species can be kept.

5 .Riparium:A terrarium which replicates a Riverbank or ditch is known as riparium.

Educational Significance:

This teaching aid is helpful in

1. Studying the various kinds of plants and animals in their natural habitat.

2. Understanding the interdependence and interrelationship among plants and animals.

3. Understanding growth, development, behavior and feeding habits of different animals.

4. Exploring the similarities and differences between plants and animals.

5. Studying the diversity of organism.

4. HERBARIUM

A Herbarium a collection of pressed and dried herbs placed in an enclosure. These specimens

may be the whole plant or a part of the plant such as leaves, twigs, flowers, stem. The main

objective of having herbarium is to maintain a record of the specimens and they are often used

as reference material in describing plant taxa. They are usually kept in dried form and mounted

on a sheet of paper.



Preparation of Herbarium:

The collected plant material (from the field) are spread on sheets of newsprint or rough books

and dried. Usually they are dried in a plant press, between blotters or absorbent papers. Little

amount of boric powder may be sprinkled on the sheets to avoid insects and growth of moulds.

These sheets are kept under heavy press for drying. The sheets can be changed every day till

the specimen is completely dried.

Mounting:

The dried specimen are now transferred to a mounting sheet. The herbarium sheets are

available in the market, or you can take a standard sheet of 11 X 26 14 inches which is thick.

Place the specimen on the herbarium sheet properly and with the help of tape fix it on the sheet.

After mounting the specimen label it properly. The labeling should have the following

information.

On the right hand side

1. Common name

2. Botanical name

3. Name of the collector

4 Place of collection or locality

5. Family

6. Date of collection

After mounting arrange them in an order.

Storing:

Keep the herbarium in a big box of wood or cardboard. Naphthalene balls can be used to avoid

mites or fungal growth. After this keep the box safety in the cupboard.

Educational Significance:

The herbariums have the following educational significance.

1. It helps to identify different types of plant species.

2 .The variability of the form in the plants and their natural distribution can be studied.

3 They represent a historical record of change in vegetation over time.

4 It can represent the record of the plant, in cases where the plants becomes extinct.

5. Environmental scientists can make use of data to track changes in climate and human

impact.

6. They are very useful for research purpose.

7. They can also prove very useful as source of plant DNA for use in taxonomy and molecular

systematic.

8. They also develop interest and curiosity in the students.

IMPROVISATION OF TEACHING AIDS

An Unesco source Book for science Teaching has remarked that "Necessity is the mother of

invention; new emerging needs of science teaching therefore, call for improvisation"

The above quotation of UNESCO suits a country like India very well. With the emerging new

needs and the exploration in both knowledge and population, there is need to full fill the

demands of both. That is we have to educate an enormous pop tion with little resource in order



stand tall among the developed countries, so that should be a way out to impart effective and

efficient education, with little resource that are available. We can very easily prepare ordinary

laboratory apparatus from simple articles found in homes and other places. The only thing

required is the ingenuity and resourcefulness of the teacher and his willingness to do work. A

teacher with some ingenuity and manual skill will be able to make a number of valuable and

serviceable article. Tin cans, wires from discarded devices, pumps, parts of cars, boxes, radio,

tubes and the fike can all be made use of in providing valuable experiences. Great Scientists

like Edison, Priestley, Madame curie, Dalton and others had no big funds to provide themselves

with expensive apparatus and elaborate laboratories. They carried out their experiment most-

Successfully in the humblest of condition, with homemade and crude apparatus. If all the school

going children are to be trained in the scientific method as they should be large amount of

money will have to be set apart-for building well equipped laboratories. It is doubtful that such

provision can be made in India for decades to come. One way out of this economies problem is

improvisation of apparatus.

Every science room should therefore be equipped with a workbench and a kit of tools that may

be used by pupils and teachers in making and improvising equipment for science teaching.

Definition of improvisation

The term improvisation stands for "providing, making or doing something quickly, in the time of

need, using whatever happens to be available."

Some of the definitions of improvisation are

1. A stimulated situation to demonstrate and impart learning in respect of controls and

operations with low cost things

2. A contrived situation created out of readily available material for the sake of convenience.

3. A make-shift arrangement to accomplish the intended learning task.

4 A term which refers to the preparation of aids with simple and readily available inexpensive

material by the student and teachers.

Need for improvisation

We need improvised apparatus because

1. of the financial constraints.

2. To work within our limited Resources.

3. To develop practical skill in the students.

4. To make the students learn by action.

5. To full fill the curiosity of the students.

6. To satisfy the natural urge of the students.

7. To nurture the creativity of the students.

8. To familiarize them with the process of development of the simple apparatus. .

9. To place the student in the place of scientists

10. To provide them hands on experience in the construction of the apparatus.

11. To ignite spark of scientific thinking in their minds.

12. To inspire them to carry on their activities and experiences in the future also.



13. To place them in the place of an inventor.

14. To design experiment with handmade apparatus. .

15. To provide direct illustration of the principles involved

16. To produce cheap apparatus.

17. To produce local apparatus.

Development of low cost material

The different steps involved in the development of of low- cost material is as follows

1. Definition of Objectives: Objectives are defined in terms of the

a. knowledge to be imparted

b. Skill to be developed.

C Attitude to be developed.

d. Needs of the learner.

E Needs of the user.

f. Material to be developed.

2. Preparation of the design: A design for the development of different materials is decided in

terms of type of the material to be developed, its cost, relevance and the resources available in

the local market.

3. Development of the material: After finalizing the design, the materials are developed by the

student, teachers, and experts in cooperation with each other.

4. Pilot testing of the material : This is done by the teachers or researchers with selected sample

users. On the basis of the results of pilot testing necessary improvements or modifications are

made in the materials. Pilot testing also provides feedback to modify the objectives.

5. Finalization of the material : After modifications, if the material is satisfactory, it is finalized for

production.

6. Production and distribution : The material now is produced in large scale and then it is

distributed to different schools.

Flow Chart for the development of low-cost Materials

Values of improvised apparatus:

The Improvised apparatus have the following values

1. Economic value: The improvised material have economic value in the sense that

A The material that is produced is cheap.

B It provides the amenities of life at the cheaper rate

C . It make the school self sufficient.



. d. They does not need maintenance.

2. Educational and psychological value: It has the following educational and psychological

value

a.It is based on the psychological and educational principle that understanding travels from

hands to the head.

b. It is based on the psychological principle of co-ordination of hands and head for better

understanding

C. It provide a deeper understanding of the whole principle involved in making a particular

apparatus.

d. It provides an opportunity to the pupils to handle the apparatus, prepare models etc.

e.It instill a kind of self confidence in the pupils.

f. It satisfies the constructive skill of pupils,

g It nurtures the constructive skill of the pupils.

h. It provides an opportunity to the student to explain something new.

i. It provide then a chance to apply the principles learned.

j. It provide an opportunity for the exercise and development of ingenuity and resource fullness.

k. It develops critical thinking in the students.

1. It develops scientific thinking in the students.

m. It develops scientific attitude in the students.

n.It gives a chance to realize the difficulties faced by the scientist in inventing something new.

o. It develops independent thinking in the students.

p. It solves the problem of leisure.

Q . It solves the problem of indiscipline

3. Social value :

Improvisation helps in inculcating the following social values in the students

a. Dignity of labour

B.Co-operation with others

c. Sacrifice

d.Remove the barrier between mental and manual labour

e. Respect for others

f. habits formed, and attitude developed here can be transferred to daily life situations.

4. Recreational value :

It has the following recreational values

a. It provides them to unwind

b.It solves the problem of leisure

c.It provides an opportunity to appreciate the beauty of truth and sacrifice

5. Scientific value:

Improvisation instill the following scientific value in the student.

a. It develops scientific temper.

b.It develops interest in scientific activities.



c. It develops scientific attitude.

d.It helps in the attainment of scientific knowledge.

6. Inspiration: Improvisation instill inspiration in following way

a. It inspire them to discover something

b.It inspire them to explore

c. It inspire them to invent

d.It inspire them to become great scientist in future

e. It inspire them to lead a simple life and work within the means.

Characteristics of improvised Apparatus:

The improvised apparatus have the following characteristics:

1. The local environment with free of cost or at low cost.

2. It does not need any special skill in making and it can be made by the teachers and students

easily.

3. It can be efficiently used by the teachers and pupils to clarify the set objectives.

4. The process involved in making is simple and inexpensive.

5. The material is simple, and appropriate to the age of the student.

6. The material stimulus thinking, experimenting or further study,

7. The production of material is not time consuming. raw material easily available in the

Advantages of improvised apparatus:

There are many advantages of improvised apparatus like

1. They are cheaper

2. Can be produced locally with readily available material

3. The problem of finance can be solved.

4. It has educational value as student can learn the underlying principle on their own.

5. It make the student resourceful.

6. It provides them a sense of accomplishment.

7. It increases the constructive and creative instinct of the students

8. It inspire them to explore, discover and invert new things.

9. It is based on the psychological principle of leaning by doing

10. It provides them an opportunity to show their talent and initiations

11. It develops scientific attitude.

12. It develops scientific and critical thinking.

13. It solve the problem of leisure.

14. It has recreational value.

15. It develops dignity of labour.

16. It make student industrious.

17. It removes the barrier from manual and mental work.

18. It develops positive attitude.

19. It helps in the attainment of scientific knowledge

20. It inspire them.



Problems in the development of low cost materials:

The following are the problems in the development of low- apparatus.

1 Reluctance of the teachers.

2Reluctance of the Administrators.

3Inadequate skills of the teachers.

4 Lack of free materials.

5Lack of free facilities.

6Lack of awareness of the resources

7Lack of initiativeness of teachers

8available in the local market.

8. Lack of imitativeness of Administrators.

9. Lack of resourcefulness of teachers.

10. Lack of time.

Tools required for Improvisation (NCERT)

Description Quantity

B. 1 Hammers ball pein 8 oz. 2

2.Hammers cross pein 8 oz 2

3. Hammers claw 1

4. Screw driver heavy duty 12" 2

5. Hammers cross pein 402 2

6. Screw driver light duty 8" 2

Screw radio repairers thin 6" with insulated blade 3

8. Screw driver (watch makers set of 8) 1

9. Pliers combination Mechanics 6" 3

10. Pliers needle nose round 1" 2

Pliers needle nose round 4" 2

12. Cutting pliers 6" 2

13. Adjustable crescent wrench 10" 1

Adjustable crescent wrench 4" 1

B.15 Pipe wrenches 10" 1 (desirable

B.16. Double ended spanners white worth size 1/8" to 3/8" 1

17.Hack saw frame (hand) 12" with 2 blades - 12" XX" X 38 teeth 2

18. Fretsaw frame (wood) with blades 1

19. Panel saw wood 20" 1

20. Tenon saw 12" 1

21Kay hole saw adjustable 2

22. Block plane metal 6"-2" blade 2

23. Smoothing plane 10"-2" blade 1

24. Side plane 6" 1

25. Chisels wood 1/3" **, X", 1" 2 each

26 3/8" cold chisels metal cutting 3

Hand drilling machine gearded capacity y" drill 2

Twist drill bits parallel shank 1/16", 3/32", 1/8", 5/32" 1 set

Carborundum sharpening stone 6" X 2" (one side medium, other side fine) 2



1. Improvised Slide Projector: Take a cardboard box and make a hole on one side. Stick a

convex lens of 10 cm focal length to cover the hole. Cut the opposite side of the box and cover it

with tracing paper to work as a screen. Fix a pair of telescopic cardboard tubes of maximum

length of 20 cm. over the lens. Make arrangement for holding a film slide on the other hand of

telescopic tube. Illuminate the slide with a hundred watt milky lamp. Adjust the telescopic tubes

by sliding them to get a clear image on the tracing paper screen.

Documents

UNIT -3 TEACHING LEARNING MATERIAL